This invention relates to regulator circuits.
Switching regulators using silicon controlled rectifiers as the series switching element are gated into conduction at various rates. A common frequency is that of the AC line mains frequency or twice the mains frequency for full-wave rectified input voltages. Because the switching rate is relatively slow, relatively large filter capacitors are used.
Upon initial application of AC line mains voltage, large inrush currents may develop to charge the initially uncharged filter capacitors. To limit the peak inrush current, a series impedance such as a resistor, or thermistor inductor, may be used. Using a resistor undesirably dissipates power and reduces the regulation range. Using an inductor may require one with a relatively large and expensive core cross-section to prevent saturation of the core by the inrush current. Similarly costly is the use of a thermistor.